/*
 * 代号：凤凰
 * http://www.jphenix.org
 * 2014-06-10
 * V4.0
 */
package com.jphenix.clazz;

import java.io.DataInputStream;
import java.io.IOException;

import com.jphenix.standard.docs.ClassInfo;

/**
 * <code>LineNumberTable_attribute</code>.
 * @author mabg
 */
@ClassInfo({"2014-06-10 19:55","LineNumberTable_attribute"})
public class LineNumberAttribute extends AttributeInfo {
    
    /**
     * The name of this attribute <code>"LineNumberTable"</code>.
     */
    public static final String tag = "LineNumberTable";

    LineNumberAttribute(ConstPool cp, int n, DataInputStream in)
        throws IOException
    {
        super(cp, n, in);
    }

    private LineNumberAttribute(ConstPool cp, byte[] i) {
        super(cp, tag, i);
    }

    /**
     * Returns <code>line_number_table_length</code>.
     * This represents the number of entries in the table.
     */
    public int tableLength() {
        return ByteArray.readU16bit(info, 0);
    }

    /**
     * Returns <code>line_number_table[i].start_pc</code>.
     * This represents the index into the code array at which the code
     * for a new line in the original source file begins.
     *
     * @param i         the i-th entry.
     */
    public int startPc(int i) {
        return ByteArray.readU16bit(info, i * 4 + 2);
    }

    /**
     * Returns <code>line_number_table[i].line_number</code>.
     * This represents the corresponding line number in the original
     * source file.
     *
     * @param i         the i-th entry.
     */
    public int lineNumber(int i) {
        return ByteArray.readU16bit(info, i * 4 + 4);
    }

    /**
     * Returns the line number corresponding to the specified bytecode.
     *
     * @param pc        the index into the code array.
     */
    public int toLineNumber(int pc) {
        int n = tableLength();
        int i = 0;
        for (; i < n; ++i) {
            if (pc < startPc(i)) {
                if (i == 0) {
                    return lineNumber(0);
                }else {
                    break;
                }
            }
        }
        return lineNumber(i - 1);
    }

    /**
     * Returns the index into the code array at which the code for
     * the specified line begins.
     *
     * @param line      the line number.
     * @return          -1 if the specified line is not found.
     */
    public int toStartPc(int line) {
        int n = tableLength();
        for (int i = 0; i < n; ++i) {
            if (line == lineNumber(i)) {
                return startPc(i);
            }
        }
        return -1;
    }

    /**
     * Used as a return type of <code>toNearPc()</code>.
     */
    static public class Pc {
        /**
         * The index into the code array.
         */ 
        public int index;
        /**
         * The line number.
         */
        public int line;
    }

    /**
     * Returns the index into the code array at which the code for
     * the specified line (or the nearest line after the specified one)
     * begins.
     *
     * @param line      the line number.
     * @return          a pair of the index and the line number of the
     *                  bytecode at that index.
     */
    public Pc toNearPc(int line) {
        int n = tableLength();
        int nearPc = 0;
        int distance = 0;
        if (n > 0) {
            distance = lineNumber(0) - line;
            nearPc = startPc(0);
        }

        for (int i = 1; i < n; ++i) {
            int d = lineNumber(i) - line;
            if ((d < 0 && d > distance)
                || (d >= 0 && (d < distance || distance < 0))) { 
                    distance = d;
                    nearPc = startPc(i);
            }
        }

        Pc res = new Pc();
        res.index = nearPc;
        res.line = line + distance;
        return res;
    }
}
